Pros: I'm using these with high-power rechargeable AA-batteries in the toys of my kids. (Recharging is easy and quick.) The weight of these 'batteries' is also lower, so toys don't get to heavy. An extra plus, rechargeable batteries don't start to leak when they're empty so unused toys don't get damaged.

Cons: The snap-construction isn't easy to open for kids. The minus-side is slightly sunken in the case, so you must use it in a device with a spring on the minus.

Other Thoughts: Maybe design a container that also can contain AAA-batteries, so no problems occur with the plus and minus terminals.

Bottomline: Perfect for toys, less weight and no leaking if you use rechargeable batteries.

Pros: -Use your mountain of AA's you have around in place of C's
-Use cheaper AA rechargeables instead of expensive C rechargeables (that also need a larger charger)
-Great price (for 5!)

Cons: -AA's are a little longer than C batteries, so not a perfect fit
-it is questionable as to how long the hinges will hold up, but a piece of tape should hold them easily if the hinges fail.

Other Thoughts: -These do NOT impede the connection between my AA's (rechargeables) because of the plastic-plastic contact on either end.
-Make sure your AA's have the standard "post" or "bump" on the positive side--if it's too short, they may not contact.
-Most items that take C batteries often have large springs in the battery bay, so the extra mm of the AA vs C battery should not be a problem for most devices.

Bottomline: Get these, some of the D converters, and rechargeable AA's, and you're all set for most type of batteries. (Now we just need a capacitor system or something for 9v!)

Pros: Lets you use cheap AA cells in place of expensive C cells.
Can be easily altered to work properly.

Cons: Instead of the more typical adapter that just expands the diameter, this model also has a small piece of plastic on each end of the battery making the battery longer.
This also means that if 2 or more of these adapters will be placed in a row, these plastic ends mean that there will be no contact between batteries since they are too far apart.

Other Thoughts: These are allmost useless since they have plastic that cover some of the front and back of the AA cell so that it cannot get proper contact in the battery compartment.
However, they can be altered by cutting the ends off and will work properly.

Bottomline: These are great, but you will need to cut them down quite a bit or they will not work at all.

Pros: I bought these for use with the DX Mammoth HF-22 Cree Q2 LED flashlight SKU.13930 which was the last unit on offer. Hehehe. Instead of buying C cell batteries which dont last as long and which is more expensive, I bought these AA to C converters to do the job.
Build quality is much better than the AA to D cell converter but its still a semi flimsy joint for the two halves of the holder.
Works well but just remember that the AA size is aboout 5mm longer than the C size cells.

Cons: Also semi flimsy joint on the two halves of the converter which might break after prolonged opening and closing of the converter to charge the batteries.

Other Thoughts: Hopefully DX will bring in better quality battery converter models in future.

Bottomline: Bought two of these 5-packs as I needed to use 6 cells with the DX Mammoth HF-22 Cree Q2 LED flashlight.